Change docker entry point script to allow additional commands (#403)

* Change docker entry point script to allow additional commands

* Delete Dockerfile

.azure/Dockerfile

@@ -1,25 +0,0 @@
-FROM ubuntu:18.04
-
-# Set shell
-SHELL ["/bin/bash", "-o", "pipefail", "-c"]
-
-# Docker
-RUN apt-get update && apt-get install -y --no-install-recommends \
-        apt-transport-https \
-        ca-certificates \
-        curl \
-        gpg-agent \
-        software-properties-common \
-    && curl -fsSL https://download.docker.com/linux/ubuntu/gpg | apt-key add - \
-    && add-apt-repository "deb https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable" \
-    && apt-get update && apt-get install -y --no-install-recommends \
-        docker-ce \
-    && rm -rf /var/lib/apt/lists/*
-
-# Build Tools
-RUN apt-get update && apt-get install -y --no-install-recommends \
-        wget patch vim cpio python unzip rsync bc bzip2 ncurses-dev sudo \
-        git make g++ file perl bash binutils locales qemu-utils bison flex \
-    && rm -rf /var/lib/apt/lists/*
-
-WORKDIR /build

scripts/entry.sh

@@ -4,4 +4,10 @@ set -e
 # Run dockerd
 dockerd -s vfs &> /dev/null &
 
-exec bash
+if CMD="$(command -v "$1")"; then
+  shift
+  exec "$CMD" "$@"
+else
+  echo "Command not found: $1"
+  exit 1
+fi